cronic: document the bash 3.2 requirement; fix the tense of a test comment

cronic

@@ -14,6 +14,8 @@
 # --duplicate-stderr options, which may be given in any order.
 # The options and the treatment of execution traces are documented in function
 # `cronic_help`; run `cronic --help`.
+# This script runs under bash 3.2, which is /bin/bash on macOS, so it uses a
+# feature of a later bash only after checking the version.
 
 # Exit if a command exits with a non-zero status, and treat unset variables
 # as an error.
@@ -200,8 +202,8 @@ cronic_pattern=$(cronic_trace_pattern)
 if [ -n "$cronic_pattern" ] && grep -q "$cronic_pattern" "$cronic_trace"; then
   # `|| true` because `grep -v` exits with status 1 when it selects no lines,
   # which happens whenever stderr consists only of trace lines.  Without it,
-  # `set -e` would abort the script here, before it produces its report,
-  # exits with the wrapped command's status, and removes its temporary files.
+  # `set -e` would abort the script here, before it produces its report, and
+  # it would exit with status 1 rather than with the wrapped command's status.
   grep -v "$cronic_pattern" "$cronic_trace" > "$cronic_err" || true
 else
   cronic_err=$cronic_trace

tests/cronic-test/cronic-test.sh

@@ -6,9 +6,10 @@
 #
 # `cronic` filters trace lines out of stderr with `grep -v`, which exits with
 # status 1 when it selects no lines.  `cronic` runs under `set -e`, so an
-# unguarded `grep -v` aborted the script at that point:  no report was printed,
-# the exit status was grep's 1 rather than the wrapped command's, and all of
-# the temporary files under /tmp were left behind.
+# unguarded `grep -v` would abort the script at that point:  no report would be
+# printed, and the exit status would be grep's 1 rather than the wrapped
+# command's.  (The temporary files would still be removed, by `cronic`'s EXIT
+# trap, so the left-behind-files check in `check` does not detect that bug.)
 
 set -eu